The present invention relates to a tip turbine engine, and more particularly to a particle separator for deflecting particles away from a core airflow inlet of a tip turbine engine.
An aircraft gas turbine engine of the conventional turbofan type generally includes a forward bypass fan, a low pressure compressor, a high pressure compressor, a combustor, a high pressure turbine, and a low pressure turbine, all located along a common longitudinal axis. The low and high pressure compressors are rotatably driven to compress entering air to a relatively high pressure. This high pressure air is then mixed with fuel in the combustor, where it is ignited to form a high energy gas stream. This gas stream flows axially aft to rotatably drive the high pressure turbine, which rotatably drives the high pressure compressor via a high pressure shaft. The gas stream leaving the high pressure turbine is expanded through the low pressure turbine, which rotatably drives the forward bypass fan and low pressure compressor via a low pressure shaft.
Although highly efficient, conventional turbofan engines operate in an axial flow relationship. The axial flow relationship results in a relatively complicated elongated engine structure of considerable longitudinal length relative to the engine diameter. This elongated shape may complicate or prevent packaging of the engine into particular applications.
A recent development in gas turbine engines is the tip turbine engine. Tip turbine engines locate an axial compressor forward of a bypass fan which includes hollow fan blades that receive airflow from the axial compressor therethrough such that the hollow fan blades operate as centrifugal compressors. Compressed core airflow from the hollow fan blades is mixed with fuel in an annular combustor, where it is ignited to form a high energy gas stream which drives the turbine that is integrated onto the tips of the hollow bypass fan blades for rotation therewith as generally disclosed in U.S. Patent Application Publication Nos.: 20030192303; 20030192304; and 20040025490. The tip turbine engine provides a thrust-to-weight ratio equivalent to or greater than conventional turbofan engines of the same class, but within a package of significantly shorter length.
In conventional gas turbine engines, particles entering the engine pass through the bypass fan before entering the core airflow inlet, which may be the inlet to the low pressure compressor. Particles entering the engine will be thrown radially outwardly by the rotation of the bypass fan blades and will therefore pass radially outwardly of the core airflow inlet. Thus, the dirt or other particles will not erode the compressor blades and vanes, turbine blades and vanes, and rub strips and any cooling passages and air passages will not become clogged.
However, in the current tip turbine engines, the core airflow inlet is forward of the bypass fan. Air flows directly into the core airflow inlet without first passing through the bypass fan. There is not currently any protection to keep particles from entering the core airflow inlet.